The Dutch atmospheric instrument Tropomi is ready for launch and has succesfully been attached to its satellite, Sentinel 5p. Later this year, the satellite and instrument will undergo an extensive test program to make sure they are fit to fly to space in the spring of 2016. ‘Completing the assembly is an important milestone towards the mission that will monitor air quality around the globe’, sais project manager Harry Förster of the Netherlands Space Office (NSO).

Tropomi is the only payload on board Sentinel 5 precursur. Assembly took place at Airbus Defence and Space in Stevenage, England. ‘A crucial moment for the mission team was the attachment of the cooler to Tropomi’, explains Dirk Slootweg, deputy project manager of Airbus Defense and Space Netherlands, the main contractor for this earth observation mission. ‘In space, the cooler dissipates heat from important elements of Tropomi like the detectors. The cooler had to fit seamlessly, because unlike some other satellite and instrument parts, it can’t be altered. It was a perfect fit, which shows that the preparations and production process were excellent.’

No surprises
Assembly started on May 15 and took three weeks. When completed, thermal blankets were attached to Tropomi to protect the instrument against extreme temperature variations in space. When in the sun, the satellite experiences temperatures of +130 degrees Celsius, in the shade the temperature will drop to 130 degrees below zero.

Sentinel 5p will be shipped from Stevenage to Toulouse at the end of July for a test program. Both the satellite and Tropomi undergo the sound and vibrations of a rocket launch. The pair is also tested for functionality in the vacuum and extreme temperatures of space.

‘I expect no surprises at these tests. We have great confidence in Tropomi’, sais Slootweg. ‘All individual parts have been tested thoroughly. Now they will have their final exam in the flight configuration. If all goes as planned, Tropomi and its satellite will be shipped back to the United Kingdom early December.’

Daily measurements
After some final adjustments and the flight acceptance review in Stevenage, the satellite will be shipped to Plesetsk in Russia, to be launched on board a Rockot somewhere between March and July 2016.

Tropomi is successor to other successful Dutch satellite instruments like OMI en Sciamachy. It measures carbon monoxide, methane, nitrogen dioxide, ozone and many other trace gasses in the atmosphere. Each day Tropomi produces a map of air quality around the globe, with details as small as a couple of city blocks.

Small and precise
Tropomi compares light reflected by earths atmosphere with direct sunlight by using mirrors, an ‘immersed grating’ and – in the end – a detector. Dutch innovations like the immersed grating, created by SRON and TNO, have downsized the instrument forty times compared to its predecessors, upholding and even enhancing precision and image quality. Data gathered by Tropomi in space will be interpreted by KNMI and SRON and made available for scientific research and other applications.